Percussive fuse for projectiles



Dec. 9, 1941. 1 E. REMoNDY 2,265,195

PERGUSSIVE FUSE FOR PROJCTILES Filed Feb. 25, 1959 Patented ec. 9, i941 UNETED STATES PATET OFFEC PERCUSSIVE FUSE FOR PROJECTILES Application February 25, 1939, Serial No. 258,554 In France February 26, 1938 8 Claims.

In U. S. Letters Patent No. 2,054,510, dated September 15, 1936, there is described a very sensitive percussion fuse, called a dissociable striker fuse which operates in an entirely novel manner on the reaction shock principle, the said fuse having the advantage of a particularly appreciable simplicity of manufacture and assemblage.

In U. S. Letters Patent No. 2,137,983, dated November 22, 1938, there is then described an improved form of construction of the said fuse characterized by a novel constitution and arrangement of the striker which permits a considerable reduction in weight both of the latter and of the members with which it is associated.

The present invention relates to an even more improved form'of construction, having the advantage of permitting a still further reduction in weight of the striker, and the additional advantage of facilitating the operation of the fuse, even when the impact is effected against a more or less resilient or soft obstacle, the said improvements having altogether the effect of considerably increasing the sensitiveness of the fuse in all cases.

The form of construction referred to is more particularly characterised by the employment, severally or jointly, of the following dillerent means: l

l. The striker has the form of a simple nail having a large, thin and resilient head, the said head being secured, in any suitable manner, by its outer edge to the front part of the fuse so as to hermetically close the forward end of the fuse body.

2. If necessary, and with a view to facilitating both its deformation on impact and the dissociation which has to be eiected at the moment 'of the reaction shock producing the separation of the elements of the striker, the head of the latter may be weakened at one or more points in any suitable manner.`

3. For ensuring safety on the departure of the projectile and during a certain time of flight, it is possible to interpose between the head of the striker and the element against which said head is forced in order to produce the reaction shock ensuring the dissociation of the elements of the striker, a compressible or eaceable spacing washer, the effacement being produced in this latter case either by heating (fusible washer), or under the action of centrifugal force (washer adapted to slide or fragment), or under the action of both effects combined.

4. Finally in order to ensure operation of the fuse upon impact even against an obstacle of low density or one which is compressible, resilient or the like, such as grass or moss, for example, the head of the striker is either made of such a shape, or has a brittle auxiliary element added thereto of such a character, that there is exerted by the striker, after impact, a sudden trigger effect which is effective to produce a reaction shock of the desired magnitude, even though the resistance of the obstacle itself should be insuilicient to produce that shock unassisted.

Although various structural forms of the invention are shown in the accompanying drawing and described hereinafter by way of example, it is understood, of course, that these structures may be modified in their constructional details or completed by any appropriate accessory device without departing from the invention.

In this drawing:

Figures 1, 2 and 3 are sectional elevations showing the stages in the operation of one form of fuse embodying the invention.

Figures 4 and 5 show, the first in plan and the second in section on the line V-V of Figure 4, a striker the head of which comprises weakening recesses.

Figure 6 is a section of a form of construction comprising a compressible safety Washer.

Figure 7 isa section of a form of construction comprising a safety washer adapted to be effaced under the action of heat. Y

Figures 8 and 9 show the first two stages of the operation of a, fuse having an additional trigger effect, the said trigger effect resulting from the shape of the striker head. l

Figures 10, 11, 12 and 13 show four'fdevices whereby it is possible, by means of brittle auX- iliary elements, to obtain the desired additional trigger effect.

Figures 14 and 15 show two forms of construction comprising strikers having Weighted stems.

Figure 16 shows a form of construction in which the striker head permits simplified assemblage.

Figure 17 shows the fuse of Figure 16 provided with an external protection Washer.

Figures 18 and 19 are perspective views, partly broken away, of two strikers, the heads of which comprise locally weakened portions for facilitating the operation of the fuse.

As will be seen in the gures, especially in Figure 1, the fuse according to the invention comprises a striker l having the form of a simple nail, the large, thin and resilient head 2 of which is applied to a shoulder 3 of the fuse body 4 and is held in place in any appropriate manner, as by means of a beading of varnish or mastic 5, a certain appropriate space or distance e being provided between the head 2 at the plane of its junction with the stem of the striker and the plane surface 8 adjacent the entrance of the passage 6 into which the striker stem projects and at the lower end of which is situated the percussion cap 1.

According to the showing of Figure 2, the first effect of the impact of the vprojectile against an obstacle is to drive the striker towards the percussion cap while producing' a corresponding deformation of the head 2, but this movement alone is not sufficient to cause the fuse to operate in view of the fact that the space or distance a between the plane surface 8 and the percussion cap is slightly greater than, or isat least equal to, the length of the striker stem. That is to say, the space or distance e between the head 2 and the surface 8 is preferably less than the distance between the point of the striker stem and the percussion cap when the parts are in their normal at rest positions, so that when the deformable, resilient head 2 assumes the position shown in Figure 2, the striker cannot directly contact the percussion cap.

The operation of the fuse vis effectively pro.. duced, in accordance with the principle of the dissociable'striker, only by the separation of the striker from its head, which separation is produced at the moment the said head abuts against the plane surface 8 and due to that fact, is subjected to a reaction shock suillcient to produce the desired detachment indicated in Figure 3.

To increase the sensitivity of the fuse and facilitate initial resilient deformation of the striker head, it is possible, in accordance with the showing of Figures 4 and 5, to weaken the head 2 of the striker by providing therein recesses 9, the eifect of which, from the point of view of flxing the striker head to the fuse head, is compensated by the addition of a marginal flange Il.

In general, safety at the time of departure of the projectile from the gun is adequately ensured by the fact that, at that moment, the forces acting on the striker are insufficient to produce the reaction shock which is indispensable for effecting operation of the fuse.

Under the influence of the increasing acceleration at the time of firing the projectile, the striker head is progressively deformed, but its deformation is arrested by the surface 8 before the lower end of the striker stem contacts the percussion cap, as indicated in Figure 2. During the ensuing flight of the projectile, however, the inherent resiliency of the striker head 2 automatically returns it toits original position as shown in Figure 1, that is to say, to the position which it has to occupy in order that effective operation may be produced upon impact.

However, if it desired to ensure additional safety, it is possible -to provide one or the other of the devices shown in Figures 6 and 7. L

In the first of these devices, there is disposed between the head 2 of the striker and the plane surface 8 of the fuse body a compressible washer I l made of any suitable spongy material, such as blotting paper, felt or the like, adapted to resist slightly the initial resilient deformation of the striker head, but likewise adapted to harden suiflciently when it is further compressed, upon impact and during the second stage of operation of the fuse, to act relatively to the striker the part normally played by the plane surface 8. and in such a manner that the reaction shock resulting in dissociation of the striker stem from its head is produced against the said compressed washer the centrifugal force, its elements collecting in the cavity I3 provided for receiving them.

When it is desired to produce a fuse which is automatically deprimed at the end of a certain time of flight after being fired, in order, for example, to prevent accidents that might be caused by projectiles used in anti-aircraft ring which do not make impact until they return :to the ground, the shoulder l may be made of readily fusible material 32, the disappearance of which no longer leaves the edge of the striker head fixed to the fuse body at the distance e from the surface 8, and thereby renders theoperation of the fuse impossible in practice.

This latter safety feature may also be attained by providing conductivity cores 33 in the fuse body made of suitable metal (sodium, for example) and intended to cause the heat produced by the friction of the air against the outer wall of the fuse to penetrate to the vicinity of the percusslon cap. When this heating is sumcient, the percussion cap will ignite automatically and cause the destruction of the projectile.

` When the obstacle impacted by the projectile is soft, the reaction of such obstacle is not sumciently violent to produce against the plane surface 8, immediately after impact, the reaction shock which is necessary for producing the dissociation of the striker.

It is then necessary to provide an additional arrangement whereby the deadened resistance of the impacted obstacle is converted by a trigger effect into a live reaction capable of giving rise, upon engagement of .the striker head with the plane surface 8, to a reaction shock suilicient to produce the dissociation of the striker.

To this end, it is possible to employ any one of the various devices shown in Figures 8, 9, l0, 11, 12 and 13.

In the device shown in Figures 8 and 9, the

striker head is given a normally convex shape which enables it to resist a slight pressure, but which, when the pressure involved attains a sumcientl value, will cause the head suddenly to change its shape by passing from the convex shape I4 to the concave shape I5, in accordance with a well-known phenomenon.

Of course, the magnitude of the space or distance e between the plane of junction of the striker head and stem and that of surface 8 should be so selected that, at the moment of the aforesaid deformation, the desired shock is produced against said surface.

In the form of construction shown in` Figure 10, a washer I6 made of a brittle, moderately strong material, such as glass, gum lac or the like, is provided above the striker head 2.

This washer will resist the contact of a soft obstacle until the latter, in compressing, offers suiiicient resistance to cause fracture which, being produced suddenly, will permit the accumulated energy to act eectively on the striker.

In the form of construction shown in Figure 11, there is provided a cone I1 of brittle material interposed between the striker head and the plane surface 8.

In the form of construction shown in Figure 12, the striker is normally held against inward movement by a steel needle I8 which fractures suddenly when the pressure exerted on the striker head, in gradually increasing, attains suflicient value.

In the form of construction shown in Figure 13, the striker is yieldably retained in normal position by a ball i9 pressed against it by a spring 20.

Theoretically, the trigger effect resulting from this last device may not appear sumcient, but in practice it gives the desired result.

Furthermore, the same trigger effect is partly produced in all cases due to the cushion of compressed air which is formed in the cup-shaped portion 30 of the fuse head between the front of the striker head and the front edge 3| of the fuse body.

This compressed air also assists in the projection of the striker in the same way as a solid element acting locally in the centre of the striker head.

The form of construction shown in Figures 14 and 15 corresponds to the case where it is desired that the fuse shall operate even in the case of low residual velocities.

In this case, in order that the fuse may operate, it is necessary to increase the weight of the stem of the striker.

Although the sensitivity of the fuse is thus somewhat reduced, in that it requires a greater resistance by the obstacle impacted to overcome the inertia of the striker, the certainty of operation is increased because the additional weight of the stem more than compensates for the decrease in striking force exerted against the percussion cap which would otherwise result from the lower velocity.

To obtain the necessary increase in weight, it is possible, in accordance with what is shown in Figure 14, to screw on the stem of the striker an additional weight 2|, the diameter of the latter being, of course, less than that of the passage li,l

or, in accordance with what is shown in Figure 15, to crimp on the grooved part 22 of the striker an additional mass 23, the passage 6 being preferably given a conical or iiared shape for facilitating the movement of the mass 23.

When it is desired to simplify manufacture, it is possible to employ a form of construction according to that shown in Figure 16.

In this form of construction, a striker having a normally convex head is employed, the outer edge of the head resting directly on the plane surface 8, suicient clearance being left between the edge of the striker head and theundercut portion 25 of the wall defining the side of the recess in the fuse body in which the striker head is mounted to enable the head to atten on impact without meeting with any resistance on the part of said wall.

In this case, there is no trigger effect, but the rapidity with which ythe head of the striker is forced back on impact against the plane surface 8 is suicient to produce the necessary dissociation.

If it is desired to render the shock on the striker still more violent, it is possible to dispose in front of the latter a rigid washer 26, as shown in Figure 17, which will act on the striker by rebound, in a similar manner to that produced between a stationary mass and a moving mass which collides against the former.

It is known, in fact, that after the impact, the mass which was stationary moves, while the mass in movement stops or at least loses the major part o! its momentum, the latter having served to project with energy the mass which was stationary.

The shock Ithus applied suces to produce the operation of the fuse.

Furthermore, the plate 26 protects the striker during the manipulations of the fuse, or of the projectile on which the fuse is fitted.

Figure 18 shows in perspective, but partially sectioned, a striker in which the head is provided with a weakening groove 21 for facilitating its deformation at the moment of impact.

Figure 19 is a smaller view of a striker the head of which comprises an edge 28 of reduced thickness for producing the same result.

What is claimed:

1. In a percussive fuse for projectiles of the character described, a fuse body, a percussion cap mounted in said fuse body, a striker member comprising a stem having an inner end adapted to ignite the fuse by contact with said percussion cap and a relatively thin head of substantially greater diameter than said stem deformable upon contact with an obstacle, and means carried by said fuse body adapted to abut said striker member adjacent the junction between said head and stem for preventing deformation of said head from its normal shape beyond a predetermined amount, said head and stem being normally connected to one another but the mass of said stem and strength of'its connection to said head being such that, when upon impact of the projectile said head is so far deformed as to bring it into forcible engagement with said abutment means which is still moving forwardly with the projectile, the inertia of said stem is suicient to separate it from said head and bring it into contact with said percussion cap, the normal distance between the inner end of said stem and said cap when said parts are at rest being greater than the distance through which the striker member moves in passing from its normal position to that in which separation of said stem and head occurs.

2. A percussive fuse according to claim 1 wherein the outer edge of said striker head is Xed to and closes the forward end of the fuse body.

3. A percussive fuse according to claim 1 wherein said striker head is weakened structurally at appropriate places to reduce its resistance to deformation and to dissociation of said head and stern.

4. In a percussive fuse for projectiles of the character embodying a fuse bodyhaving an enlarged recess formed in the nose thereof, a percussion cap mounted therein rearwardly of said recess and a passageway of substantially smaller diameter than said recess leading from the latter to said percussion cap, the combination of a striker member comprising a stem entering said passageway and adapted to ignite the fuse by contact with said percussion cap and a relatively thin, resilient head of approximately .the same diameter as said recess deformable upon contact with an obstacle, an abutment surface formed interiorly of said fuse body adjacent the entrance to said passageway, said head and stem being normally integral with one another but adapted to dissociate -when upon impact of the projectile said head is deformed from its normal shape suii'iciently to bring said head into effective engagement with said abutment surface which is still moving forwardly with the projectile, whereupon the reactive force due to the inertia of said striker stem separates ythe latter from said head, and means fixing the outer edge of said head against axial movement inwardly relatively to the fuse body in such position that, when the fuse is in assembled, at rest condition, the distance between said percussion cap and the adjacent end of said striker stem is greater than the distancebetween said abutment surface and the junction "of said striker stem and head.

5. In a percussive fuse for projectiles of the character embodying a fuse body having an enlarged recess formed in the nose thereof, a. percussion cap mounted therein rearwardly of said recess and a passageway of substantially smaller diameter than said recess leading from the latter to said percussion cap. the combination of a striker member comprising a stem entering said passageway and having an inner end adapted to ignite the fuse by contact with said percussion cap and a relatively thin, resilient head of substantially greater diameter than said stern separably connected to the latter, the outer edge of said head being fixed against inward axial movement relatively to said fuse body but said head being otherwise capable of deformation from its normal shape under the influence of an axially directed force imposed thereon, and means carri'ed by the fuse body for abutting the striker head adjacent its junction with said stem and preventing deformation thereof beyond a predetermined amount, the mass of said stem and strength' of its connection to said head being such that, when upon impact of the projectile said head is so far deformed as to bring it into forcible engagement with said abutment means which is still moving forwardly with the projectile, the inertia of said stem is sufficient to separate it from said head and bring it into contact with said percussion cap, the normal distance between the inner end ofsaid stem and said cap when said parts are in assembled, at rest condition being greater than the distance between said abutment means and the junction of said stem and head.

6. In a percussive fuse for projectiles of th'e character embodying a fuse body having an env larged recess formed in the nose thereof, aperto said percussion cap. the combination of s striker member comprising a stem entering said passageway and adapted to contact said percussion cap upon impact and a relatively thin. resilient head of approximately the same diameter as said recess. an abutment surface formed interiorly of said fuse body adjacent the entrance to said passageway, means fixing the outer edge of said head to the wall of said recess in such position that the junction between said head and stem is normally spaced from said abutment surface, said head and stem being normally integral with one another but adapted to dissociate when said head is deformed from its normal shape upon impact suiliciently to bring said head forcibly inw effective engagement with said abutment surface, and means interposed between said head and said abutment surface for preventing deformation of said head suiiiciently to effect said dissociation until after the projectile is in flight.

'7. A percussive fuse acrding to claim 6 wherein the deformation preventing means consists of a washer made of a material which is fusible by th'e heat of friction produced by iiight of the projectile through the air.

8. In a percussive fuse for projectiles of the character embodying a fuse body having an enlarged recess formed in the nose thereof, a percussion cap mounted therein rearwardly of said recess and a passageway of substantially smaller diameter than said recess leading from the latter to said percussion cap, the combination of a striker member comprising a stem entering said passageway and adapted to contact said percussion cap upon impact and a relatively thin, resilient head of approximately the same diameter as said recess, an abutment surface formed interiorly of said fuse body adjacent the entrance to said passageway, means fixing the outer edge of said head to the wall of said recess in such position that the junction between said head and stem is normally spaced from said abutment surface, and a compressible member interposed between said head and said abutment surface and resisting deformation of said head, said head and stem being normally integral with one another but adapted to dissociate when said head is deformed from its normal shape upon impact sufiiciently to substantially solidify said compressible member and thereby bring said head forcibly into engagement with a substantially solid abutment.

MARIE LoNIE ARBEY. l GEORGES HENRI RMONDY.

Legal representatives of the estate of Lon Emile Rmondy, deceased. 

